Fiber reinforced composite materials containing reinforced fibers and a matrix resin have a high specific strength, a high specific modulus, excellent mechanical characteristics, and high performance characteristics such as weather resistance and chemical resistance, and thus such materials have received attention in the use of aircraft parts, automobile parts, construction materials, and sports goods and have been increasingly demanded with the years.
Prepregs for fiber reinforced composite materials are manufactured by, for example, impregnating reinforced fiber tow or cloth with an uncured thermosetting resin or applying thermosetting resin powder to reinforced fibers or cloth thereof and then melting the resin powder under a pressure so as to impregnate the fiber structure with the resin. However, prepregs manufactured in these methods cannot be easily handled. For example, such prepregs are adhesive and are hard to work into complicated shapes.
Reinforced fibers include inorganic fibers such as glass fibers and carbon fibers and organic fibers such as aramid fibers. Furthermore, reinforced fibers are broadly divided into continuous fibers and discontinuous fibers depending upon the usage patterns. Continuous fibers are at least several meters in length. Molded components made of fiber reinforced composite materials containing continuous fibers as reinforced fibers are manufactured by, for example, a hand lay-up method or an autoclave method. In the hand lay-up method, continuous fibers processed on woven clothes such as textile fabrics and knitted fabrics are coated with an uncured thermosetting resin with a brush or a roller, and then the thermosetting resin is cured to manufacture molded components. In the autoclave method, a required number of prepregs impregnated with an uncured thermosetting resin are stacked on continuous fibers and then are heated and pressed by an autoclave to manufacture molded components. Discontinuous fibers are obtained by cutting continuous fibers to several millimeters to several centimeters and are called chopped fibers or cut fibers. For example, in the hand lay-up method, molded components made of fiber reinforced composite materials containing discontinuous fibers as reinforced fibers are manufactured by regularly or irregularly orientating discontinuous fibers in a mold and then applying an uncured thermosetting resin with a brush or a roller before curing of the thermosetting resin. Alternatively, molded components are manufactured by heating and pressing, in a mold, a sheet molding compound (SMC) material prepared by mixing an uncured thermosetting resin and discontinuous fibers beforehand or a bulk molding compound (BMC) material prepared by mixing an uncured thermosetting resin and discontinuous fibers beforehand.
In the method of manufacturing molded components made of an SMC material or a BMC material with discontinuous fibers used as reinforced fibers, reinforced fibers are impregnated with a resin beforehand and thus the steps are simplified (the step of injecting a resin is eliminated) with high productivity. Furthermore, the short reinforced fibers facilitate the passage of the material so as to manufacture molded components in complicated shapes. These characteristics allow this method to be widely used for manufacturing construction materials such as a bath tub and automobile parts such as a spoiler.
An SMC material is particularly a sheet material having a thickness of several millimeters. Reinforced fibers including glass or carbon fibers cut to 10 mm to 50 mm are dispersed at random or in one direction on an uncured thermosetting resin sheet made of materials such as polyester resin and vinyl ester resin. In the method of manufacturing molded components made of an SMC material (SMC method), the SMC material disposed in a mold is heated and pressed to have a larger size. This passes the material into a final shape and cures the material by heat, thereby manufacturing a molded component. The SMC method is similar to metal press molding and thus has been widely used for manufacturing automobile parts such as a hood and a door panel.
In addition to prepregs obtained by impregnating continuous fibers with an uncured thermosetting resin, a known material containing continuous fibers as reinforced fibers is obtained by stacking a thermoplastic resin sheet and textile fabrics (woven clothes) including thermoplastic resin fibers and reinforced fibers or a mixed yarn thereof, and heating and pressing the sheet at a specific temperature (For example, see Japanese Patent Laid-Open No. 63-87228).
The use of a thermoplastic resin as a matrix resin leads to various choices of a matrix resin and allows the use of a high-performance resin called an engineering plastic. This may widen the application of a fiber reinforced composite material. Moreover, the use of a thermoplastic resin considerably shortens a molding cycle as compared with the use of a thermosetting resin and thus is expected to be applied to a fiber reinforced composite material for mass-produced items of automobiles.
Carbon fiber reinforced thermoplastics (CFRTP) containing carbon fibers as reinforced fibers and thermoplastic resins of nylon, polycarbonate (PC), and so on as matrix resins can be flexibly molded into complicated shapes by injection molding. In other words, CFRTP has high moldability. Thus, CFRTP has been recently used for components of electric or electronic equipment such as a personal computer, OA equipment, a digital camera, a digital video camera, a cellular phone, audiovisual equipment, a telephone, a facsimile, an electrical appliance, and a toy, or cabinets that accommodate these components and dense packaging circuits (For example, see Japanese Patent Laid-Open No. 2004-358828).
However, a main unit serving as the cabinet of electric or electronic equipment requires a thick portion called a boss or a rib that is integrated with the main unit so as to connect a component of the electric or electronic equipment and the main unit. It has been quite difficult to form a fiber reinforced composite material containing continuous fibers as reinforced fibers into a thick portion such as a boss or a rib. For this reason, a boss or a rib additionally molded onto the top surface of the cabinet with an adhesive or the like contains a thermoplastic resin as a matrix resin and is made of a fiber reinforced composite material containing discontinuous fibers as reinforced fibers (For example, see Japanese Patent Laid-Open No. 2004-358828).
As has been discussed, if the cabinets of electric or electronic equipment such as a personal computer, OA equipment, a digital camera, a digital video camera, a cellular phone, AV equipment, a home appliance, and a toy are made of a fiber reinforced composite material, the fiber reinforced composite material needs to be molded into a fine and complicated shape called a boss or a rib. However, it has been quite difficult to form a fiber reinforced composite material containing continuous fibers, which have more excellent mechanical characteristics than discontinuous fibers, as reinforced fibers into a boss or a rib. Thus, a boss or a rib made of a fiber reinforced composite material containing discontinuous fibers as reinforced fibers is additionally molded onto the top surface of a cabinet with an adhesive or the like. Unfortunately, the boss or the rib molded onto the top surface with an adhesive or the like is likely to be broken from the top surface at the basal portion of the boss or the rib by a concentrated stress. Prioritizing moldability, a thermoplastic fiber reinforced composite material containing discontinuous fibers as reinforced fibers may be molded into a cabinet including a boss or a rib. A fiber reinforced composite material containing discontinuous fibers as reinforced fibers has less excellent mechanical characteristics such as a tensile strength than a fiber reinforced composite material containing continuous fibers as reinforced fibers. Thus, also in this case, the boss or the rib is likely to be broken from the top surface at the basal portion of the boss or the rib by a concentrated stress.
The present invention has been devised to solve the conventional problem. An object of the present invention is to provide a molding method for a fiber reinforced composite material and a molding apparatus for the fiber reinforced composite material, by which a thick portion such as a boss or a rib with a fine and complicated shape can be integrally formed with a molded component concurrently with the main unit of the molded component.